I have an Access violation on this line :
if (RTT.wgl.wglBindTexImageARB(RTT.wgl.hBuffer, WGL_FRONT_LEFT_ARB) == FALSE)
ShowMessage(AnsiString().sprintf("wglBindTexImageARB returned %i", GetLastError()));
The exception is thrown before the getlasterror() call : so getlasterror can't tell anything.
When I try to evaluate the expression with Borland Builder's debugger, it says impossible to evaluate : due to WGL_FRONT_LEFT_ARB not defined.
So I added wglext.h in the includes : no success, same debugger message.
But perhaps is it a C++ syntax problem or Borland logic not respected ?
Here are extracts of my code :
UnitGLForm.h :
#include <GL/gl.h>
#include "glext.h"
#include "wglext.h"
class TGLForm : public TForm
{
__published: // Composants gérés par l'EDI
void __fastcall FormCreate(TObject *Sender);
private: // Déclarations de l'utilisateur
HDC ghDC;
bool bSetupPixelFormat(HDC hdc,HDC hdc2);
public: // Déclarations de l'utilisateur
__fastcall TGLForm(TComponent* Owner, class CPreviewCallback *delegatePreview, HDC hDC);
virtual void DrawScene();
};
struct GLRenderToTexture
{
struct
{
HDC hdc;
HGLRC hGlRc;
HPBUFFERARB hBuffer;
PFNWGLGETEXTENSIONSSTRINGARBPROC wglGetExtensionsStringARB;
PFNWGLCHOOSEPIXELFORMATARBPROC wglChoosePixelFormatARB;
PFNWGLCREATEPBUFFERARBPROC wglCreatePbufferARB;
PFNWGLGETPBUFFERDCARBPROC wglGetPbufferDCARB;
PFNWGLQUERYPBUFFERARBPROC wglQueryPbufferARB;
PFNWGLDESTROYPBUFFERARBPROC wglDestroyPbufferARB;
PFNWGLRELEASEPBUFFERDCARBPROC wglReleasePbufferDCARB;
PFNWGLBINDTEXIMAGEARBPROC wglBindTexImageARB;
PFNWGLRELEASETEXIMAGEARBPROC wglReleaseTexImageARB;
} wgl;
unsigned int uintTexture; // the texture we're going to render to
};
GLRenderToTexture RTT;
HDC ghDC2;
HGLRC ghRC;
So it seems for me logic that I can access to RTT, ghDC2, ghRC from any other .h or .cpp file. Follows here the implementation :
UniGLForm.cpp :
__fastcall TGLForm::TGLForm(TComponent* Owner, class CPreviewCallback *delegatePreview, HDC hDC)
:TForm(Owner)
{
ghDC2 = hDC;
this->DoubleBuffered = true;
}
//---------------------------------------------------------------------------
bool TGLForm::bSetupPixelFormat(HDC hdc,HDC hdc2)
{
PIXELFORMATDESCRIPTOR pfd, *ppfd;
int pixelformat;
ppfd = &pfd;
ppfd->nSize = sizeof(PIXELFORMATDESCRIPTOR);
ppfd->nVersion = 1;
ppfd->dwFlags = PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER | PFD_TYPE_RGBA;
ppfd->dwLayerMask = PFD_MAIN_PLANE;
ppfd->iPixelType = PFD_TYPE_COLORINDEX;
ppfd->cColorBits = 8;
ppfd->cDepthBits = 16;
ppfd->cAccumBits = 0;
ppfd->cStencilBits = 0;
if ( (pixelformat = ChoosePixelFormat(hdc, ppfd)) == 0 )
{
MessageBox(NULL, "ChoosePixelFormat failed", "Error", MB_OK);
return false;
}
if (SetPixelFormat(hdc, pixelformat, ppfd) == FALSE)
{
MessageBox(NULL, "SetPixelFormat failed", "Error", MB_OK);
return false;
}
if ( (pixelformat = ChoosePixelFormat(hdc2, ppfd)) == 0 )
{
MessageBox(NULL, "ChoosePixelFormat 2 failed", "Error", MB_OK);
return false;
}
if (SetPixelFormat(hdc2, pixelformat, ppfd) == FALSE)
{
MessageBox(NULL, "SetPixelFormat 2 failed", "Error", MB_OK);
return false;
}
return true;
}
//---------------------------------------------------------------------------
void __fastcall TGLForm::FormCreate(TObject *Sender)
{
ghDC = GetDC(Handle);
if (!bSetupPixelFormat(ghDC, ghDC2)) Close();
ghRC = wglCreateContext(ghDC);
wglMakeCurrent(ghDC, ghRC);
InitializeGL();
// pixel buffer
RTT.wgl.wglChoosePixelFormatARB= (PFNWGLCHOOSEPIXELFORMATARBPROC)wglGetProcAddress("wglChoosePixelFormatARB");
RTT.wgl.wglGetExtensionsStringARB= (PFNWGLGETEXTENSIONSSTRINGARBPROC)wglGetProcAddress("wglGetExtensionsStringARB");
RTT.wgl.wglChoosePixelFormatARB= (PFNWGLCHOOSEPIXELFORMATARBPROC)wglGetProcAddress("wglChoosePixelFormatARB");
RTT.wgl.wglCreatePbufferARB= (PFNWGLCREATEPBUFFERARBPROC)wglGetProcAddress("wglCreatePbufferARB");
RTT.wgl.wglGetPbufferDCARB= (PFNWGLGETPBUFFERDCARBPROC)wglGetProcAddress("wglGetPbufferDCARB");
RTT.wgl.wglQueryPbufferARB= (PFNWGLQUERYPBUFFERARBPROC)wglGetProcAddress("wglQueryPbufferARB");
RTT.wgl.wglDestroyPbufferARB= (PFNWGLDESTROYPBUFFERARBPROC)wglGetProcAddress("wglDestroyPbufferARB");
RTT.wgl.wglReleasePbufferDCARB= (PFNWGLRELEASEPBUFFERDCARBPROC)wglGetProcAddress("wglReleasePbufferDCARB");
RTT.wgl.wglBindTexImageARB= (PFNWGLBINDTEXIMAGEARBPROC)wglGetProcAddress("wglBindTexImageARB");
RTT.wgl.wglReleaseTexImageARB= (PFNWGLRELEASETEXIMAGEARBPROC)wglGetProcAddress("wglReleaseTexImageARB");
int pixelFormats;
int intAttrs[32] ={WGL_RED_BITS_ARB,8,
WGL_GREEN_BITS_ARB,8,
WGL_BLUE_BITS_ARB,8,
WGL_ALPHA_BITS_ARB,8,
WGL_DRAW_TO_PBUFFER_ARB, GL_TRUE,
WGL_BIND_TO_TEXTURE_RGBA_ARB, GL_TRUE,
WGL_SUPPORT_OPENGL_ARB,GL_TRUE,
WGL_ACCELERATION_ARB,WGL_FULL_ACCELERATION_ARB,
WGL_DOUBLE_BUFFER_ARB,GL_FALSE,
0}; // 0 terminate the list
unsigned int numFormats = 0;
// get an acceptable pixel format to create the PBuffer with
if (RTT.wgl.wglChoosePixelFormatARB(ghDC, intAttrs, NULL, 1, &pixelFormats, &numFormats)==FALSE)
ShowMessage(AnsiString().sprintf("wglChoosePixelFormatARB returned %i", GetLastError())); // GetLastError will tell us why it failed
//Set some p-buffer attributes so that we can use this p-buffer as a 2d texture target
const int attributes[]= {WGL_TEXTURE_FORMAT_ARB, WGL_TEXTURE_RGBA_ARB, // p-buffer will have RBA texture format
WGL_TEXTURE_TARGET_ARB, WGL_TEXTURE_2D_ARB, 0}; // Of texture target will be GL_TEXTURE_2D
// the size of the PBuffer must be the same size as the texture
RTT.wgl.hBuffer= RTT.wgl.wglCreatePbufferARB(ghDC, pixelFormats, ClientWidth, ClientHeight, attributes);
RTT.wgl.hdc= RTT.wgl.wglGetPbufferDCARB(RTT.wgl.hBuffer);
RTT.wgl.hGlRc= wglCreateContext(RTT.wgl.hdc);
// so that we can share textures between contexts
wglMakeCurrent(NULL, NULL);
if (wglShareLists(ghRC,RTT.wgl.hGlRc) == FALSE)
SCmsgError(AnsiString().sprintf("wglShareLists returned %i", GetLastError())); // GetLastError will tell us why it failed
}
//---------------------------------------------------------------------------
void TGLForm::DrawScene()
{
wglMakeCurrent(ghDC, ghRC);
ClientWidth = 1920;
ClientHeight = 1080;
// create a texture to use as the backbuffer
glGenTextures(1, &RTT.uintTexture);
glBindTexture(GL_TEXTURE_2D, RTT.uintTexture);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
// make sure this is the same color format as the screen
glTexImage2D(GL_TEXTURE_2D, 0, 4, ClientWidth, ClientHeight, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
// switch to the texture context
wglMakeCurrent(RTT.wgl.hdc, RTT.wgl.hGlRc);
glEnable(GL_TEXTURE_2D); // Enable Texture Mapping
TGLBlend::SetBlendMode(0);
glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE,GL_MODULATE); //ARC
glClear(GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-1.0, 1.0, -1.0, 1.0, -1.0, 1.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glClearColor(0,0,0,1);
glClear(GL_COLOR_BUFFER_BIT);
glDisable(GL_TEXTURE_2D);
// switch back to the screen context
wglMakeCurrent(ghDC, ghRC);
TGLBlend::SetBlendMode(0);
glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE,GL_MODULATE); //ARC
glClear(GL_DEPTH_BUFFER_BIT);
glViewport(0, 0, ClientWidth, ClientHeight);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-1.0, 1.0, -1.0, 1.0, -1.0, 1.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
wglMakeCurrent(RTT.wgl.hdc, RTT.wgl.hGlRc);
glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, RTT.uintTexture);
PaintGL();
glDisable(GL_TEXTURE_2D);
wglMakeCurrent(ghDC, ghRC);
glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, RTT.uintTexture);
RTT.wgl.wglBindTexImageARB(RTT.wgl.hBuffer, WGL_FRONT_LEFT_ARB);
// set up some vertices to render a texture to a model; example:
glBegin(GL_QUADS);
glColor4ub(255,255,255,255);
glTexCoord2f (0.0, 0.0); glVertex2f (-1.0, -1.0);
glTexCoord2f (1.0, 0.0); glVertex2f (1.0, -1.0);
glTexCoord2f (1.0, 1.0); glVertex2f (1.0, 1.0);
glTexCoord2f (0.0, 1.0); glVertex2f (-1.0, 1.0);
glEnd();
RTT.wgl.wglReleaseTexImageARB(RTT.wgl.hBuffer, WGL_FRONT_LEFT_ARB);
glDisable(GL_TEXTURE_2D);
glFlush();
SwapBuffers(ghDC);
}
=> this copy of PaintGL to the texture and then textured to a quad works perfectly.
The problem is when I want to use this texture in another window :
UnitGLForm2.h :
class TGLForm2 : public TForm
{
__published: // Composants gérés par l'EDI
void __fastcall FormCreate(TObject *Sender);
public: // Déclarations de l'utilisateur
__fastcall TGLForm2(TComponent* Owner, class CPreviewCallback *delegatePreview);
virtual void DrawScene();
};
UnitGLForm2.cpp :
__fastcall TGLForm2::TGLForm2(TComponent* Owner, class CPreviewCallback *delegatePreview)//, HDC hDC)
:TForm(Owner)
{
}
//---------------------------------------------------------------------------
void __fastcall TGLForm2::FormCreate(TObject *Sender)
{
wglMakeCurrent(ghDC2, ghRC);
InitializeGL();
}
//---------------------------------------------------------------------------
void TGLForm2::DrawScene()
{
ClientWidth = 1920;
ClientHeight = 1080;
wglMakeCurrent(ghDC2, ghRC);
TGLBlend::SetBlendMode(0);
glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE,GL_MODULATE); //ARC
glClear(GL_DEPTH_BUFFER_BIT);
glViewport(0, 0, ClientWidth, ClientHeight);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-1.0, 1.0, -1.0, 1.0, -1.0, 1.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glEnable(GL_TEXTURE_2D);
RTT.wgl.wglBindTexImageARB= (PFNWGLBINDTEXIMAGEARBPROC)wglGetProcAddress("wglBindTexImageARB");
RTT.wgl.wglReleaseTexImageARB= (PFNWGLRELEASETEXIMAGEARBPROC)wglGetProcAddress("wglReleaseTexImageARB");
glBindTexture(GL_TEXTURE_2D, RTT.uintTexture);
if (RTT.wgl.wglBindTexImageARB(RTT.wgl.hBuffer, WGL_FRONT_LEFT_ARB) == FALSE)
SCmsgError(AnsiString().sprintf("wglBindTexImageARB returned %i", GetLastError())); // GetLastError will tell us why it failed
glBegin(GL_QUADS);
glColor4ub(255,200,200,200);
glTexCoord2f (0.0, 0.0); glVertex2f (-1.0, -1.0);
glTexCoord2f (1.0, 0.0); glVertex2f (1.0, -1.0);
glTexCoord2f (1.0, 1.0); glVertex2f (1.0, 1.0);
glTexCoord2f (0.0, 1.0); glVertex2f (-1.0, 1.0);
glEnd();
RTT.wgl.wglReleaseTexImageARB(RTT.wgl.hBuffer, WGL_FRONT_LEFT_ARB);
glDisable(GL_TEXTURE_2D);
glFlush();
SwapBuffers(ghDC2);
wglMakeCurrent(NULL,NULL);
}
Including a header is not enough. You also have actually load the extension. Everything related to PBuffers is a extension and thus must be loaded in a special way. Google for "OpenGL extension loading"